When you say everyone has their own printer what do you mean? How many printers do you have, are they connected to the workstations or the server? Have you created a different printer for each user using the same LPT1 port on the server?
Where does the DOS program reside, on the server or the workstation? If it is on the server why do you have to use the net use command to print to a local port? If the DOS program is on the workstation why the necessity for the terminal session?
Sorry but you're all over the map. A little more concise detail please.
reply to NetUseQs
Each person needs a network printer on their desk, the kind with a network card and a static IP address assigned to it.
Then, the terminal server needs all 3 printers installed, direct by IP.
Then, in each person's logon script, add this...
RUNDLL32 PRINTUI.DLL,PrintUIEntry /y /n "name_of_printer"
...this ensures their own printer is set as their default (cause terminal server will always mess with you and make the last printer installed the default)
If the DOS program only recognizes LPT printers, then your going to have to assign 1 printer to LPT1, the other to LPT2, and so on, then have the DOS program default to LPT1, 2 or 3. If it won't do this, your out of luck, run the DOS program on the individual's workstation then.